Method of and apparatus for extruding metal collapsible tubes



A ril 11, 1961 J. D. MARTIN 2,979,195

METHOD OF AND APPARATUS FOR EXTRUDING METAL COLLAPSIBLE TUBES Filed Sept. 26, 1956 5 Sheets-Sheet 1 FIG.|

April 11, 1961 J. D. MARTIN 2,979,195

METHOb OF AND APPARATUS FOR EXTRUDING METAL COLLAPSIBLE TUBES Filed Sept. 26, 1956 3 Sheet s-Sheet 2 \\\\H I 1 FIG] ,0

i m I G .6 IIIIIIII/I l I70 l I W0 W4 J Y v i J. D. MARTIN Aprii 11, 1961 METHOD OF AND APPARATUS FOR EXTRUDING METAL COLLAPSIBLE TUBES Filed Sept. 26, 1956 5 Sheets-Sheet 3 FIGQIO m gg United States atent r 2,979,195 Patented Apr. 11, 1961 METHOD OF AND APPARATUS FOR EXTRUDING METAL COLLAPSIBLE TUBES Joseph D. Martin, Far Hills, N.J., assignor, by mesne assignments, to The Procter & Gamble Company, Cincinnati, Ohio, a corporation of Ohio Filed Sept. 26, 1956, Ser. No. 612,150

3 Claims. (Cl. 207--6) This invention relates to methods of and apparatus for making metal collapsible tubes and more particularly such tubes having a main body of substantially elliptical cross section or a cross section of other configuration in which one axis is substantially greater than the other. Tubes of this character are disclosed in the patent to Deskey No. 2,718,983, granted September 27, 1955. Also the invention encompasses a novel construction of such a tube which may be used for the packaging of pastes, creams and fluid preparations, such as tooth paste, shampoo, and the like. In the production of tubes of the character indicated having a wall thickness of about .005 to .007 of an inch, on a regular commercial scale, difliculties have been encountered due to the tendency of the walls of the tubes to become wrinkled, torn, cracked or otherwise distorted or injured in the course of impact extrusion. This is particularly true of such a tube which is provided with a downwardly curved or sloping shoulder extending from the base of the neck to the main tube wall. It is especially true of tubes of this character having walls of conventional thickness and formed of the softer and more readily fiowable metals such as lead, tin and alloys containing large percentages of lead or tin or both.

Experience with production of tubes of the types indicated has led to the conclusion that the tendency of the walls to become wrinkled or otherwise damaged, in the course of extrusion, has been due to the initial, more rapid flow of the metal through the extrusion gap in the region of the major axis, i.e. at the points of sharper curvature of a tube of elliptical cross-section. In turn, this is apparently due to the fact that a conventional fiat slug, placed in the female die and subjected to the impact of the male die, is first bent downwardly upon being struck adjacent its center by the tip or nose of the punch. This tends to urge upwardly to a certain extent the portions of the slug in the region of the ends of the major axis. As a result, these portions are subjected to extrusion slightly sooner than those portions in the region of the minor axis so that the upflow of metal in the first mentioned portions serves to exert a distorting and tearing force on the more slowly moving metal in other regions of the tube wall. These tearing and distorting forces appear to have a more disturbing effect upon the softer metals mentioned than upon harder metals, such as aluminum.

It has been a primary object of the present invention to bring about as nearly as practicable, the simultaneous upflow of the metal in all regions of the tube wall. Various expedients have been devised for this purpose, all being directed to the retardation of the initiation of upflow of the metal in the regions of sharpest bending or curving of an elliptical tube wall, i.e. adjacent the ends of the major axis of a cross-section through the tube. One such expedient is the formation of the male and female dies in such a manner that the wall thickness of the extruded tube will be somewhat, say 20 to 30%, greater in the regions mentioned than in the less sharply curved regions, or those adjacent the minor axis of the tube cross-section. The greater volume of metal required to form a given area of the wall of greater thickness serves to retard the rate of upflow sufiiciently to bring about substantially uniform upflow of metal in all regions of the tube wall.

Another expedient toward the foregoing end involves rounding off of the annular corner adjacent the lower end of the male die or punch, which defines the inner edge of the extrusion gap, in the regions adjacent the ends of the major axis of the cross-section of the punch. This results in a retardation of the impact, and hence the flow of metal, in those regions without materially increasing the wall thickness in those regions.

Still another expedient which may be employed is to form the slugs of'varying thickness. Thus, if the slugs are made slightly thinner in the regions at the ends of the major axis of the ellipse, or the like, than in the region of the minor axis, substantially simultaneous upward extrusion may be brought about around the entire periphery of the slug and the extrusion orifice.

A further expedient toward the same end utilizing a slug of uniform thickness throughout, is to modify the surface of either the female die cavity or the outer surface of the male die, or both, which form the extrusion orifice so as to retard slightly the upflow of the metal in the regions adjacent the ends of the major axis of the ellipse. This may be achieved either by roughening slightly the portions of one or both of those surfaces in the indicated regions or by lessening the frictional resistance in the regions adjacent the ends of the minor axis of the ellipse, as 'by chromium plating the surfaces in the latter regions.

A still further expedient, which enables the use of a slug of uniform thickness throughout, involves the formation of the bottom surface of the die cavity of the female die and the cooperating surface at the lower end of the male die which serve to form the shoulder at the top of the finished tube, so that a slightly smaller clearance will be provided between these surfaces at the end of the downstroke of the male die in the region of the midportion of the slug than adjacent its more sharply curved ends. This will result in substantially simultaneous upward extrusion of the metal around the entire periphery of the slug. It will be understood that when this expedient is employed the shoulder of the finished tube will be slightly thinner in the region adjacent the minor axis than in the regions adjacent the ends of the major axis. Other objects, features and advantages of the invention will appear from the detailed description of various illustrative forms of the same which will now be given in conjunction with the accompanying drawings, in which:

Fig. 1 is a top View of a filled and closed tube constructed in accordance with the invention, said tube a being of substantially elliptical cross-section;

Fig. 2 is a front elevational view of said tube;

Fig. 3 is a side elevational view of the tube;

Fig. 4 is a view showing the relationship between a punch or male die and the female die of an extrusion press employed in the production of the tube, at the instant of first contact of the male die with the slug in the female die;

Fig. 5 is a view similar to Fig. 4 but illustrating the parts in a different position in the course of the extrusion operation;

Fig. 6 is an elevational view of the lower end of a modified form of punch which may be employed in the production of the tube, looking at one of the broader faces of the punch;

Fig. 7 is a diagram illustrating the form and mode of production of the cavity in the female die for a tube of generally elliptical cross-section;

Fig. 8 is a schematic view in cross-section through the male and female dies taken at a point slightly below the top of the female die, with certain details of the male die omitted; it illustrates, on an exaggerated basis, the contour of the tube wall formed between the two dies;

Fig. 9 is a cross-sectional view through a special form of slug which may be employed in the production of the tube, this view being taken along the major axis of the slu F ig. 10 is a cross-sectional view through a modified form of female die showing the relationship thereof to the male die at the end of the downward stroke of the latter, this arrangement being adapted to form a tube having a top shoulder which is slightly thinner in its midportion than adjacent the ends of the major axis of its cross-section;

Fig. 11 is a magnified longitudinal section through a portion of the lower end of the male die of Fig. and

Fig. 12 is a similar view through a portion of the lower end of the male die of Fig. 6, taken along the major axis of the ellipse.

It will be understood that in the drawings the relationship between various dimensions has been exaggerated for the purpose of better illustration of the principles of the invention. Conventional clearances or tolerances will be provided at various points to bring about proper impact extrusion of the tubes.

In the production of tubes in accordance with the present invention any suitable form of impact extrusion press may be employed, such as that disclosed in the patent to John H. Friden, No. 2,023,879, granted December 10, 1935. In such a machine there is provided a vertically reciprocatory head mounted in suitable guideways in a frame structure and adapted to be reciprocated at a suitable speed, say 60 cycles per minute, and with sufficient force to effect extrusion of a tube from a slug of appropriate metal. As will be understood, the head referred to carries a punch forming the male die of the machine and this is moved downwardly and into the cavity in a female die which carries the slug to be extruded. As the punch engages the slug and squeezes it downwardly against the bottom wall of the cavity in the die, metal from the slug will extrude upwardly around the punch to form the main body of the tube. Partly in advance of such upward extrusion of the metal through an orifice provided between an extrusion edge or surface on the male die and the wall of the female die, and partly during such upward extrusion, the punch will force some of the metal from the slug downwardly to form the neck portion of the tube. Downward movement of the punch is so regulated that the main surface at the lower end of the punch, which is shaped to conform with the shoulder of the tube, will be stopped a slight distance above the corresponding surface at the bottom of the die cavity so that a shoulder of suitable wall thickness will be pro vided. In general, the arrangement may be such that the wall thickness of all, or at least the major portion, of the body of the tube which is extruded upwardly will be .005 to .007 of an inch. A shoulder is formed to extend from the wall of the tube to the base of the neck and this may have any suitable thickness, greater than that of the wall of the tube, to provide desired rigidity at the top of the finished tube. The .thickness of this shoulder is determined by the space between a surface adjacent the lower end of the male die and a cooperating surface at the bottom of the cavity of the female die, when the male die is at the endof its downstroke.

leans are preferably provided for automatically stripping the extruded tube from the punch and delivering it to a suitable receptacle or conveyor. For this purpose the female die may be provided with a central opening through its bottom in which is mounted a knockout pin. This pin is arranged for movement up and down under control of a suitable cam on the machine. At the beginning of the extrusion operation it extends into the cavity in the die and lends some support to the central portion of the slug. It is retracted in coordination with the downward movement of the punch to enable the formation of the neck of the tube in the manner explained. After the tube has been formed, and as the punch rises, the knockout pin is raised to engage the lower end of the neck portion of the tube and urge it upwardly to free it from its frictional engagement with the female die. The tube then continues to rise with the punch and after the latter completely clears the female die structure, it is automatically swung outwardly through an appropriate angle and air is blown through a passage extending longitudinally of the punch to blow the tube from the latter to a suitable receiving point. Appropriately cushioning means are provided for preventing damage to the rather delicate collapsible tube as it is so expelled from the punch.

Referring now to the drawings, there is shown in Figs. 1, 2 and 3 a preferred form of the tube in accordance with the invention. This tube has a main body of generally elliptical form in cross-section. It may be of truly elliptical form but, as will be explained, it is preferably of a slightly modified elliptical form. it has been found desirable to adopt a cross-section having a major axis substantially twice the length of its minor axis, but the more sharply curved portions of the Wall adjacent the ends of the major axis are more rounded than in a true ellipse. Thus the tube has two broad faces 10 curved along an arc of relatively large radius and the narrow side walls 11 curved along an arc of relatively short radius. Referring to Fig. 7, the walls 10 may suitably be curved along a radius r while the walls 11 may be curved along radius r. This modified form of ellipse simplifies the production of the dies required for the extrusion of the tube. It enables the employment of grinding equipment for this purpose of somewhat simpler construction than that required for the production of dies for a truly elliptical cross-section. However, if desired, the cross-section may be made substantially truly elliptical since equipment for the accurate formation of the necessary die surfaces is available. Also the cross-section may assume a variety of other elongated forms if desired.

The top of the improved tube is preferably provided with a downwardly curved or sloping shoulder 12, having a small central flat portion 13 from which projects the neck 14 of the tube. As shown, the shoulder preferably has a gentle slope toward its ends but it may have any slope desired. The neck, after extrusion of the tube, may suitably be provided with screw threads for the reception of an appropriate cap 15. It will be understood that in the finishing of the tube the outer end of the neck will either be trimmed off or will be tapped to provide the desired opening for discharge of the contents of the tube. The open end of the tube, which becomes its bottom, will also be trimmed off to form a tube of desired strength.

After the tube has been formed and decorated in a suitable manner, as by coating and printing upon its wall, it may be filled with the desired cream, paste, or liquid through the open bottom, the tube being inverted for this purpose, while the entire wall of the tube maintains its elliptical form. After it has been filled, the bottom is pinched together and sealed in any suitable manner. it may be folded and crimped for this purpose and if desired a clip 16 may be applied to the folded end. In lieu of this the pinched together walls of the tube at the bottom may be welded together by electrical means or the like to effect a tight and strong seal.

Turning now to Fig. 4, there is shown a male die or punch having a main body portion 17 and an end portion 17a. These may be fastened together by any suitable means capable of providing an air passage axially through the two portions of the punch. The upper end of the main body 17 may, if desired, be of circular crosssection for insertion and securement in the reciprocating head of the press. However, the lower portion of this body and the end portion 17a are provided with a contour or cross-section corresponding with the shape of the Wall of the tube to be extruded. In the illustrative example this will be of generally elliptical form. At the lower end of portion 17a there is provided a shoulder 17b corresponding with the shape of the shoulder 12 at the top of the tube. Below the shoulder 17b there extends downwardly a tip 170 adapted to form the opening through the neck of the tube. As shown in the above mentioned Friden patent, the tip 170 is preferably a separate element forming a valve around which the tube ejecting air is passed, in the manner explained. At the lower end of the side wall of punch end 17a the wall extends downwardly and outwardly at a small angle for a distance of about .015 to .032 of an inch to provide an extrusion edge 17d (Fig. 11). This edge in cooperation with the wall of the cavity in the female die defines the extrusion orifice.

In Fig. 4 the punch is shown at the point in its cycle at which the tip 170 just engages a slug 18 which has been inserted either manually or automatically in a cavity 19 in the female die 20. The contour of the slug 18 and the vertical wall of the cavity 19 correspond with the cross-sectional shape of the tube to be formed. A slight clearance is provided between the extrusion edge 17d and the wall of the cavity 19 when the edge enters the cavity to thus provide the desired extrusion orifice.

The female die 20 is retained by a die ring 21 suitably mounted on the frame of the press beneath the reciproeating punch 17. Die 20 may have a cylindrical outer wall cooperating with a corresponding inner wall in a cavity at the top of the ring 21 or, if desired, the cooperating surfaces of the die and die ring may be elliptical or of the general contour of the tube to be formed, but of somewhat greater dimension. Along the vertical axis of the die 20 there is provided an opening from the bottom of the cavity 19 to the bottom of the die. Within this opening is mounted a knockout pin 22 which cooperates with a plunger 23 arranged for veritcal reciprocation in an opening through the bottom of the die ring 21 and also an alined opening in a portion of the main frame (not shown) which supports the ring. As will be understood, by reference to the above mentioned patent to Friden, the plunger 23 is operated from a cam on the press to move downwardly in coordination with the punch 17 in the course of extrusion. When the punch reaches the lower end of its stroke the parts will assume the position indicated in Fig. 14 of said Friden patent. At an intermediate point in the course of extrusion, the parts will assume the position indicated in Fig. 5 of the present application. When the downward movement of the punch is completed, the extrusion of the tube will have been completed and the punch will shortly thereafter start its upward movement. During a limited portion of this upward movement the tube will be held frictionally by the female die, and the tip of the plunger will be retained frictionally by the neck of the tube, thereby opening the valve identified with the tip. After such limited movement, however, the knockout pin 22 will be raised by the plunger 23 to force the tube upwardly along with the punch. At this time the tube will be retained through relatively small friction forces on the punch. After the punch has been lifted above the top surface of the female die 20 it will be swung outwardly, as explained above, and air will be blown through the punch to discharge the tube into a suitable receptacle.

Now in order to avoid wrinkling or other distortion or mal-formation of the tube in the course of its extrusion, the orifice provided between the surface 17d on the male die and the wall of the cavity 19 of the die 20, is made wider in certain areas than others. This is illustrated in Fig. 8 wherein 17e indicates the crosssection of the end 17a of the punch in the region of the extrusion edge 17d. The vertical wall of the cavity 19 of die 20 is indicated at 19a. The thickness of the tube Wall formed by the extrusion is indicated at 24. It will be noted that this thickness is greater adjacent the ends of the major axis of the elliptical form, as indicated at 24a, than in the regions 24b adjacent the ends of the minor axis of the cross-section of the tube. When this cross-section is of elliptical form the portions 24a may be characterized as disposed at the more sharply curved ends while the portions 24b are disposed in the less sharply curved regions or regions of curvature along a greater radius. It has been found that in so forming the extrusion orifice and hence the tube wall, it is" possible to produce a smooth unwrinkled tube even from the soft metals and even in the formation of a tube having a curved shoulder of the character indicated at 12 in Fig. 2. The thickening of the tube wall in the regions 24a serves to retard the upward extrusion of the metal at these points due to the need for more metal per unit of area of the wall than in the thinner regions. This serves to offset the normal tendency of the punch to extrude the metal and the slug upwardly adjacent the ends of its major axis at a slightly earlier instant than in the regions at the ends of the minor axis. Good results have been obtained with a wall thickness in the relatively fiat sides 24]; of the tube, forming the major portion of the periphery,of .007 of an inch and a wall thickness in the more sharply curved, relatively minor portions 24a of the tube of between .0085 and .009 of an inch.

In Figs. 6 and 12 a different expedient for overcoming the difliculties discussed above is shown. In this embodiment of the invention the extrusion surface 1711 at the lower end of the portion 17a of the punch has the same form as the wall of the die cavity, with no attempt to widen the orifice at the ends of the major axis, but it is slightly rounded in certain regions along its lower edge as indicated at 17 These rounded regions 17 are disposed adjacent the ends of the major axis of the cross-section of the tube to be formed. A slight rounding of the extrusion edge 17d, in the manner explained, will be found to retard the upward extrusion ofthe metal in these regions sufficiently to bring about substantially simultaneous and uniform upward extrusion through all portions of the extrusion orifice. If the extrusion surface 17d has a height of between .015 and .032 of an inch the rounding ofi of the lower edge at the points 17; may extend upwardly along said extrusion surface for a distance of about .005 of an inch.

In Fig. 9 another expedient for bringing about uniform extrusion of a tube of thecharacter indicated is shown, without the need for varying the width of the extrusion orifice around the periphery of the male die. This involves the employment of a slug 18a which is slightly thicker in its mid-portion than adjacent the ends 18b of the major axis of the slug. This may be achieved by slightly curving or tapering the top surface of the slug or both the top and bottom surfaces of the slug.

When such a slug is inserted in the female die and the punch is moved downwardly into the cavity of the die an extruding pressure will be applied substantially simultaneously throughout the length of the orifice. Apparently the bending of the slug as the tip of the punch strikes its center serves to carry the portions 18b at the end of the'major axis upwardly a slight extent to compensate for the tapering form of the slug. Moreover, the thicker metal adjacent the center of the slug is forced outwardly toward the ends with the result that substantially uniform movement of the metal upwardly through all portions of the extrusion orifice takes place. achieve this purpose the slug, of conventional thickness adjacent its center, may be between .005 and .010 of an inch thinner adjacent the ends of its major axis.-

In Fig. 10 a further embodiment of the invention is illustrated, which does not require varying the width of the extrusion orifice. Here the tube shoulder forming surface 17g of the punch or male die is curved along a slightly different are from the cooperating shoulder forming surface 20b of the female die. This die may suitably be formed of two separate parts 20a and 20c, the latter being in the form of a sleeve having a press fit in relation to the part 20a which carries the shoulder-forming surface 20b. The arrangement is such that the surfaces diverge slightly toward the ends of the major axis of the cross-section of the slug and of the tube to be formed. In this way even though a slug of uniform thickness is employed, the central portion of the shoulder forming surfaces of the two dies may be made to exert an extrusion pressure on the metal of the slug at substantially the same instant that the portions of those surfaces adjacent the major axis exert such pressure. The special configuration of the surfaces 17g and 20b compensates for the bending of the slug as the tip 170 of the punch first strikes the slug. In accordance with this embodiment of the invention the curvature of the tube shoulder forming surfaces of the male and female dies may be such that the portions of these surfaces adjacent the major axis of the slug may be spaced a distance of from .005 to .010 of an inch further apart than the portion adjacent the minor axis of the slug. The two surfaces indicated may be smoothly and gradually curved or sloped to provide the relationship indicated between their end portions and their central area.

It will be understood that the average thickness of the tube shoulder throughout will be greater than that of the tube wall to provide the desired rigidity. In general the average thickness of the shoulder for all forms of the invention will be that of the conventional thickness of the shoulder on a cylindrical tube.

While a number of different methods and forms of apparatus have been disclosed for insuring uniform extrusion of the wall of a tube having a cross-section of elliptical or other elongated form it will be understood that various other expedients and modifications may be employed in accordance with the general principles of the invention.

What is claimed is:

1. A method of making a metal collapsible tube provided with a discharge nozzle projecting from an end wall formed with sloping shoulders, the body of said tube having a cross-section with a major axis substantially greater than its minor axis, said method comprising forming a slug of metal having the contour of the desired cross-section of the tube and having a slightly less thickness in the regions adjacent the ends of the major axis of its contour than adjacent the minor axis thereof, subjecting said slug while in a female die the cavity of which has in cross-section the contour of said slug to impact extrusion by forcing into said cavity and against said slug, with such a force and at such a velocity, as to effect impact extrusion of the metal of said slug, a male die having a surface at its lower end of substantially the same contour as said slug and arranged to cooperate with the surrounding wall of said female die cavity to provide an extrusion orifice therebetween, and bringing the cooperating surfaces of said male and female dies and said slug into impact extrusion relationship, the variable thickness of said slug serving to retard upward extrusion adjacent the ends of the major axis of the tube and thereby causing the metal of said slug to flow through all portions of said extrusion orifice substantially simultaneously and at the same rate outwardly along said male die.

2. Apparatus for making a metal collapsible tube provided with a discharge nozzle projecting from an end wall formed with sloping shoulders, the body of said tube having a cross-section with a major axis substantially greater than its minor axis, which comprises a female die having a cavity surrounded by a wall of the contour of said cross-section and arranged to receive a metal slug of the same contour, a reciprocatory male die arranged to be forced into said cavity and against said slug to bring about extrusion of the metal of said slug by impact, said male die having a slightly enlarged portion adjacent its free end providing a surface of substantially the same contour as said cross-section but spaced slightly inwardly from said wall of the female die when it is within said cavity thereby to provide an extrusion orifice, said orifice being wider in the regions adjacent the ends of said major axis than adjacent the ends of said minor axis, said male die having a central extension at its free end adapted to form a projection from the end wall of the tube to provide a nozzle, which extension upon striking said slug serves to bend the slug along its longitudinal axis to a greater extent than along its minor axis thereby tending to initiate extrusion adjacent the ends of said major axis slightly in advance of extrusion adjacent said minor axis, the difference in the width of said orifice provided between said wall of the female die and said surface of the male die serving to retard extrusion through portions of said orifice adjacent the ends of said major axis to bring about a substantially uniform rate of upward flow of the metal through all portions of said orifice.

3. Apparatus for making a metal collapsible tube provided with a discharge nozzle projecting from an end wall formed with sloping shoulders, the body of said tube having a cross-section with a major axis substantially greater than its minor axis, which comprises a female die having a cavity surrounded by a wall of the contour of said cross-section and arranged to receive a metal slug of the same contour, a reciprocatory male die arranged to be forced into said cavity and against said slug to bring about extrusion of the metal of said slug by impact, said male die having a slightly enlarged portion adjacent its free end providing a surface of substantially the same contour as said cross-section but spaced slightly inwardly from said wall of the female die when it is within said cavity thereby to provide an extrusion orifice, said male die having a central extension at its free end adapted to form a projection from the end wall of the tube to provide a nozzle, which extension upon striking said slug serves to bend the slug along its longitudinal axis to a greater extent than along its minor axis thereby tending to initiate extrusion adjacent the ends of said major axis slightly in advance of extrusion adjacent said minor axis, a rounded corner being provided on said surface of the male die adjacent the bottom face thereof in the regions adjacent the ends of the major axis of a cross-section through said male die to reduce flow, and said surface on said male die along the regions forming the minor axis of said cross-section and lying between the major axis thereof joining the end wall of said male die directly without rounding to create a freer flow and to thus equalize the flow characteristics of the metal forming the walls of said tube.

References Cited in the file of this patent UNITED STATES PATENTS 

